Nutrit ional Support of Repti lePatients

Ryan S. De Voe, DVM, MSpVM, DACZM,

DABVP (Avian), DABVP (Reptile & Amphibian)

KEYWORDS

� Reptile � Nutrition � Assist feeding � Nutritional support � Neonates

KEY POINTS

� Nutritional support is a very important, though often neglected, factor in the managementof sick and anorexic reptiles.

� Reptiles can benefit greatly from receiving appropriate nutritional support in a timelymanner.

� A basic understanding of reptilian metabolism, digestive physiology, and the natural his-tory of commonly encountered species can help the clinician make sensible recommen-dations for the maintenance of healthy animals and appropriate intervention in the case ofill animals.

INTRODUCTION

One of the most amazing characteristics of ectothermic animals is their gastrointes-tinal physiology and ability to efficiently process calories. Similarly sized mammalsand reptiles use dramatically discordant amounts of calories and nutrients to functionand grow. Though it is difficult to make broad statements regarding such huge andvaried taxa, a generally accepted rule of thumb is that reptiles have approximatelyone-tenth of the energy requirements of a comparably sized mammal.1,2 Becauseof the unique reptilian gastrointestinal physiology and energy metabolism, veterinar-ians are often confused about how to approach the nutritional support of ill reptiles.Many veterinarians and reptile keepers think that because reptiles in health do noteat as frequently as mammals or birds they can withstand the same kind of fastingintervals when clinically ill. Therefore, the tendency can be to allow ill reptiles to goconsiderable lengths of time before nutritional support is instituted. In many cases,short intervals of anorexia are not clinically important to the reptile but, in other cases,effective nutritional support can be the deciding factor as to whether or not treatmentis successful.

North Carolina Zoological Park, 4401 Zoo Parkway, Asheboro, NC 27205, USAE-mail address: ryan.devoe@nczoo.org

Vet Clin Exot Anim 17 (2014) 249–261http://dx.doi.org/10.1016/j.cvex.2014.01.009 vetexotic.theclinics.com1094-9194/14/$ – see front matter � 2014 Elsevier Inc. All rights reserved.

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Veterinarians will often recommend convalescing reptiles be kept at temperaturesin the upper range of their preferred optimal temperature zone (POTZ) to increasetheir metabolic rate and speed healing.3,4 The elevation in body temperature andmetabolic rate associated with healing or recovery from illness increases the reptilepatient’s caloric needs independent of any other factors affecting the animal. There-fore, it is possible for reptile patients to develop a catabolic state when environ-mental temperatures are elevated and caloric intake does not address theincreased needs.5 This same issue can occur with healthy reptiles that are kept inap-propriately warm without adequate caloric intake or which are not allowed to prop-erly thermoregulate; however, the problem can become exacerbated with ill orinjured animals.Another important factor to consider in providing nutritional support is the effect

digestion can have on metabolism in reptile patients. In several reptile species, re-searchers have documented what is referred to as specific dynamic action (SDA).6

SDA is defined as an increase in metabolism caused by the ingestion of food, espe-cially proteins, and is ubiquitous across a wide variety of animal taxa. In a study usingpythons (Python regius and P molurus) ingestion of amino acids independent of bodytemperature resulted in a postprandial rise in oxygen consumption, heart rate, andgrowth of visceral organs,7 which is representative of what has been seen in othervertebrate species. Thus, to maximize the metabolic rate and speed healing, reptilesshould be given access to temperatures in the upper end of their POTZ and be fedadequately. Meal composition has an effect on SDA in reptiles, with meals having“complete” amino acid profiles (as found in whole vertebrate prey items) elicitingmaximal effect compared with diets deficient in some amino acids. Fats and carbohy-drates do not elicit SDA in reptiles.8

Though references exist regarding reptile nutrition, there is little solid research toguide the clinician when it comes to nutritional support of the reptile patient.5 There-fore, much of what is presented in this article, though based on scientific fact, is anec-dotal and it should be applied at the clinician’s discretion according to details of theparticular case.Throughout this article, when referring to the feeding of whole prey items, it is

assumed that the prey is prekilled unless otherwise specified.

CHOICE OF FOOD FOR ASSIST FEEDING

In most cases, unless there are specific contraindications, the animal’s regular dietcan be used for assist feeding. Many lizards and chelonians that are acclimated topeople will readily accept hand feeding when they would otherwise refuse to eat.The author has seen several bearded dragons (Pogona vitticeps) and green iguanas(Iguana iguana) that become habituated to hand feeding and will refuse to eat foodnot presented by hand. Some anorexic reptiles (including snakes) will swallow afood item after it has been introduced into their mouths. One of the keys to successwith this method in snakes is to hook the snake’s teeth into the rodent so it is difficultfor them to spit it out. This technique is described in further detail in the section onnutritional management of neonatal reptiles.If the animal cannot or will not tolerate assist feeding with whole, natural food items,

those food items can be liquefied in a blender or food processor and administered viagavage or an indwelling feeding tube. It may be necessary to dilute the resultantmixture so it will pass through an appropriately sized feeding tube. The author willoften administer oral fluids as part of the treatment protocol, so the benefit of dilutingfood mixtures can be two-fold.

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Currently, several commercially available products seem appropriate for providingnutritional support to reptile patients. Oxbow Animal Health (29012 Mill Rd, MurdochNE, USA; www.oxbowanimalhealth.com) offers products formulated for herbivores(Herbivore Critical Care) and carnivores (Carnivore Critical Care). In addition, theLafeber company (24981 N. 1400 East Rd, Cornell, IL, USA; www.lafeber.com) offersa variety of products with products formulated for herbivores and carnivores, as wellas products created specifically for omnivores and piscivores. Anecdotally, theseproducts have performed well in reptile patients. In some applications, these productsoffer an advantage over whole or natural food items because they are nutrient-dense,easily digested, and assimilated (ie, hydrolyzed proteins, amino acids). All of the afore-mentioned products come in a powdered form and they are reconstituted beforeadministration. The author has occasionally experienced complications with the useof commercially available powdered diets. In these instances, following administrationof the product, the material becomes dehydrated within the stomach or intestine and itcreates an obstructive condition. This complication occurs when the patient is dehy-drated and it can be avoided by paying careful attention to maintenance of adequatehydration. In most cases, resolution of this complication has been achieved byrestoring normal systemic hydration and administration of oral fluids to rehydratethe food mass.Historically many veterinarians have relied on canned “critical care” dog or cat diets

for nutritional support of reptile patients. These foods are readily available and easy touse but may not be the best choice in most reptile cases and possibly detrimental inothers. Critical care diets are formulated to contain highly digestible and caloricallydense ingredients and many contain liver as primary ingredients. Liver is very highin purine content, which is a product of nucleotide degradation and precursor ofuric acid.9 In uricotelic reptiles, the ingestion of diets containing purine-rich ingredientswill theoretically increase uric acid production and may exacerbate existing healthconditions or create unnecessary complications. Clinicians should pay close attentionto the ingredients of products they use to provide nutritional support to their reptile pa-tients and make educated choices based on the physiology, age, and health of theparticular species.

THE MECHANICS OF ASSIST FEEDING

Before administering nutritional support to a reptile patient, the animal must be prop-erly conditioned to optimize benefit and avoid complications. First, the animal must begiven access to an appropriate thermal gradient and allowed to thermoregulate. Someanimals may not have normal mobility and, therefore, cannot behaviorally thermoreg-ulate effectively. In these cases, the clinician will have to make a best guess on whattemperature within the species POTZ the patient should be kept at. Regardless, withmost reptile patients this means warming them up. If food is administered to an animalthat has a body temperature less than what is necessary for digestion, putrefactioncan occur within the gastrointestinal tract, creating a new array of problems to dealwith. Following warming of the patient, the reptile needs to be adequately hydratedbefore feeding. If the animal is dehydrated, rehydration can be accomplished viaadministration of oral or parenteral fluids. Only after the animal has been brought toan appropriate body temperature and is considered normally hydrated should assistfeeding be attempted.As mentioned previously, many reptiles will accept assist feeding with minimal dif-

ficulty. When deciding on amethod for providing nutritional support to a reptile patient,both human and reptile welfare must be considered. Working around the oral cavity of

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many reptiles puts the handler at serious risk of injury or even death with somevenomous species (Fig. 1). Large chelonians and lizards, even if considered docile,can inflict severe wounds or even amputate digits should an accident occur duringan assist-feeding episode. The animal can suffer as well if the handling necessaryfor the assist feeding is too rough or prolonged. The author’s rule of thumb is that areptile should not be vigorously restrained for more than 5 minutes at any one time,if possible. If assist feeding takes longer than 5 minutes and/or the animal fights therestraint unrelentingly, either chemical restraint or an indwelling feeding tube shouldbe considered.As previously stated, many reptiles can be assist fed simply by hand-offering food or

placing food directly in the oral cavity. Syringe feeding a liquid diet is also possiblewhen animals will tolerate it. Some lizards and chelonians will accept syringe feeding,though ultimately it depends on the individual patient’s characteristics. When this isnot possible, tube-feeding a liquid diet is often the next option. Tube feeding a reptileis similar to tube feeding avian patients and can be accomplished using either flexibleor rigid tubes. Complications such as esophageal or gastric perforation can occur witheither type of tube, so the type of tube should be based on clinician preference andpatient characteristics. With a gentle touch, damage to the upper gastrointestinal tractdue to tube feeding is rare. The author prefers tube feeding smaller reptiles with thestainless steel gavage tubes typically used with birds (Fig. 2). Red rubber cathetersand larger rubber tubes can be used with larger patients. Care should be taken toensure that the end of the tube is smooth and is passed gently to avoid trauma tothe oral cavity, esophagus, and/or stomach. It is paramount that the animal be wellrestrained because even well-suited equipment used skillfully can cause damage tothe animal if it breaks restraint. The judicious use of an appropriate oral speculum is

Fig. 1. Use of long hemostats for safe feeding of a venomous beaded lizard (Helodermahorridum).

Fig. 2. Stainless steel feeding tubes used for gavage of small reptiles.

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also recommended to avoid a variety of potential complications. If specula are notused, flexible tubes can be bitten off and swallowed and steel gavage tubes caninduce injury to the oral or pharyngeal cavity and/or esophagus if an animal withsufficiently powerful jaws bites down on them. Oral specula also protect personnelperforming the procedure from accidental bites.When prolonged nutritional support is expected and/or the animal is difficult or

dangerous to hand or tube feed, indwelling feeding tubes are indicated (Fig. 3). Place-ment of a pharyngostomy or esophagostomy tube is a simple surgical procedurewithin the realm of capability for most veterinary clinicians. With some reptiles, theact of assist feeding can be dangerous and stressful to both the animal and thehuman. Species that possess powerful jaws equipped with sharp teeth or beaks areformidable patients. Repeat administration of food or medications can be impractical,

Fig. 3. An esophagostomy tube for long-term provision of nutritional support to a wildcommon snapping turtle (Chelydra serpentina) presented for rehabilitation. In this case,repeated feeding per os would be very stressful for the turtle and potentially dangerousfor personnel.

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stressful, unsafe, and ultimately counterproductive. Placement of a pharyngostomyor esophagostomy tube is indicated in any chronically anorexic patient that is not aserpent and that does not participate willingly in the assist-feeding process. Often,experienced reptile veterinarians will proactively place feeding tubes in anesthetizedreptiles that they suspect may be unwilling to eat on recovery and during convales-cence. In the author’s practice, this is standard procedure with wild eastern box turtles(Terapene carolina carolina) that present for rehabilitation. Animals that are willing toeat voluntarily are rarely deterred by the presence of a feeding tube. Therefore, it isimportant that the animal continue to be given the opportunity to feed normally beforeevery tube feeding. Once the animal is eating consistently, the tube can be removedand the defect will typically heal via second intention without complication.Methods of tube placement are described elsewhere in detail, so will not be dis-

cussed in this paper. When placing the tube it is paramount to carefully verify its place-ment within the gastrointestinal tract. Usually this can be accomplished by pulling thetube out of the mouth and then redirecting down the esophagus, or direct visualizationof the tube in place (using endoscopy if necessary). This step is critical to avoid thepotential complication of delivering liquid food into the subcutaneous tissues orcoelom of the patient. Another common mistake during pharyngostomy or esopha-gostomy tube placement is extension of the tube too far, resulting in perforation ofthe stomach or pressure necrosis of the gastric wall from the tube tip. The author typi-cally administers a small amount of water-soluble contrast material such as diatrizoatevia the feeding tube to verify proper placement before patient recovery from anes-thesia. Though somewhat challenging in chelonian patients, proper tube placementcan also be verified via ultrasonography. This method is made easier by flushing asmall volume of saline through the tube to ideally create some distention of the stom-ach and confidence that the tip of the tube is appropriately positioned.Maintenance of an indwelling feeding tube in reptiles can be challenging. The tube

needs to be secured in a way that the animal will not easily dislodge it. Modification ofthe animal’s environment to remove objects that the tube could be hung up on is alsoimportant. Before administration of food in to the feeding tube, it should be flushedwith water to determine patency. It is also critical that the tube be aspirated beforefeeding to make sure the previously administered meal has left the stomach and ismoving through the digestive tract appropriately. Occasionally, feeding tubes, espe-cially very small gauge tubes, will become clogged. If an obstruction occurs, gentllyflushing the tube with warm water in a pulsatile fashion may be effective in restoringpatency. Small amounts of dilute pineapple juice and/or vinegar can be routinelyflushed through the tube with the idea that it will help breakdown concretions offood material within the tube. Feeding tubes can usually be replaced without toomuch difficulty after the tissues around the stoma have healed if an obstruction isintractable to clearance.Indwelling feeding tubes are usually left in place until the reptile begins eating on its

own. Most reptile patients will eat on their own when the condition causing theanorexia is resolved, despite the presence of the indwelling feeding tube. Follwingremoval of the tube, the healed stoma can be surgically repaired; however, thisdoes not seem to be necessary as closure of the stoma usually occurs rapidly withno intervention in otherwise healthy animals.Deciding on the appropriate volume of food to deliver to a reptile via tube or assist

feeding can be difficult. Many reptile species, such as giant snakes, monitor lizards,and crocodilians, are capable of ingesting huge meals relative to their body size. How-ever, most reptile species are not capable of handling such large meals and shouldbe fed conservatively. All cases need to be evaluated on an individual basis; however,

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a good starting point is 3% of bodyweight. This means that in the case of a 100 ganimal, the initial volume of food to be delivered via tube feeding is 3 mL. This is nota perfect method because there is obviously variation in the weight of different liquiddiets but it is close enough to provide a starting point. In most cases, the volume canbe increased over time if desired. It should be understood this recommendationregarding volume of food administered is a general guideline and does not take intoconsideration nutrient density of the diet. Volume is typically the limiting factor whenproviding nutritional support to reptile patients, especially those that have beenanorexic for some time. In starved avian patients that present to the author’s wildliferehabilitation center, the same rule of thumb for determining starting volume is usedin combination with the calculated caloric requirements of the bird. In reptile patients,caloric requirements are not as well understood and vary depending on severalfactors. Therefore, the author has found providing nutritional support to reptiles basedon volume to be an easier and more practical approach.Gastrointestinal ileus is a common sequela of many conditions affecting reptile

patients. For this reason, the clinician should carefully monitor patients for evidenceof gastrointestinal dysfunction. When managing reptile cases that require nutritionalsupport, the author will routinely mix barium sulfate into liquid diets or inject it infood items to easily track the food’s transit through the gastrointestinal tract radio-graphically. This is a simple method to evaluate gastrointestinal motility and patency.Several publications report on the gastrointestinal transit time of various contrastmaterials in a variety of species. Transit times vary according to species and can rangefrom approximately 1 to 7 days.10–16

REFEEDING SYNDROME

Otherwise healthy animals that experience physiologic anorexia (as seen during hiber-nation, torpor, or breeding) do not suffer from refeeding syndrome and they can be fedwithout concern even with considerable intervals between feedings. Some adult ballpythons (P regius) will only feed for 3 to 4 months out of the year but remain healthy,maintain body condition, and suffer no consequences when they begin to eat aftermonths of anorexia. However, in animals that are ill, starved, and/or in a cachecticstate, refeeding syndrome can result in significant morbidity.5 Refeeding syndromeoccurs when the acute influx of glucose causes life-threatening hypokalemia andhypophosphatemia. Development of refeeding syndrome can be avoided by conser-vative introduction of feeding following prolonged anorexic states. In these cases, it isbest to correct any existing electrolyte abnormalities before feeding and limitation ofinitial food intake should not exceed 50% of what would be considered the animal’sdaily energy requirement.

NUTRITIONAL SUPPORT OF NEONATES

Neonatal reptiles can be tricky to manage nutritionally. Many reptiles are born or hatchwith significant caloric stores via the internal yolk sac, which in the wild provides en-ergy for dispersal before initiation of feeding. In the case of snakes, most species willgo through ecdysis shortly after hatching or birth and do not typically feed until afterthis first shed. Usually this first ecdysis occurs within 10 to 14 days; however, somespecies, such as blood pythons (P curtus spp), do not shed for the first time until 3to 5 months of age. Even with such prolonged intervals, these species do well clinicallyprovided they are kept in a suitable habitat with ready access to water.It is common to encounter neonatal reptiles suffering from acute hypoglycemia that

will benefit greatly from nutritional support. Hatchling chelonians that have struggled

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to leave the egg and/or nest can present moribund but will respond dramatically toadministration of a drop of oral 50% dextrose or other high-energy, easily absorbedfood. The author has never measured blood glucose levels in neonatal reptiles thatpresent in this condition (usually due to the diminutive size of the patient and benignnature of the intervention) but has seen many animals make surprising recoveries.Another common dilemma with neonatal reptiles is some animals simply refuse to

begin feeding following hatching or birth. Failure to begin feeding is most commonlyencountered with snake species but it can occur with any taxa. Arboreal speciesand/or species that are especially diminutive as neonates are especially problematic.In the wild, these species typically take small frogs, lizards, or even invertebrates astheir first prey, so that they do not recognize domestic neonatal mice as food is notsurprising.Several techniques are used by experienced herpetoculturists to entice anorexic

neonatal snakes to feed. The reptile veterinarian should be aware of these techniquesand implement themwhen possible. First, efforts should be made to create as suitablean environment as possible before offering the food item. The feeding attempt shouldbe made during the time of day when the species is naturally most active and the envi-ronment should be calm and quiet. Another detail that is often overlooked is where theanimal is fed. Many hobbyist publications recommend feeding reptiles outside of theirenclosures to avoid habituating the animal to expect food every time the door to thecage opens. This is fine with well-established animals but completely disruptive to ne-onates that are not feeding consistently. In addition, arboreal species are much morelikely to feed when on a comfortable perch. On the other end of the spectrum, fossorialspecies are more comfortable feeding when prey items are presented in coveredareas such as under a piece of cork bark, sheet of newsprint, or in a hide box. In sit-uations in which the prey item is being manipulated, a pair of long-handled forceps isrecommended to maintain as much distance as possible between the keeper andanimal, especially with venomous species. Many animals are not comfortable feedingin front of people and they will drop the prey item if they detect even the slightestmovement in the environment, such as a withdrawing hand or someone walkingaway from the enclosure.In cases in which an attempt is being made to feed rodent prey to a species that

would normally begin feeding on amphibians or reptiles, manipulation of scent canbe beneficial. Washing the rodent with a mild nonscented soap and rinsing thoroughlycan help temper the odor of the rodent and improve palatability. Following washing,other scents can be applied to the rodent in an effort to make it smell like a frog, lizard,or other more natural prey. Scenting of rodents can be accomplished in a variety ofways. The simplest method is to take a lizard or frog and rub it on the rodent in an effortto transfer scent. Another method involves using a blender to make a frog or lizardslurry, which is applied to the food item. The author freezes opportunistically encoun-tered road-killed frogs, toads, and lizards for this purpose. Live frogs and lizards canbe used for scent transfer but their health and welfare should always be considered aspart of the cost-benefit assessment. Pathogen transmission is possible with this prac-tice but, if common sense is used and obviously diseased lizards or amphibians areavoided, the risk is often deemed acceptable.Prekilled rodents can be manipulated to make themmore attractive prey to neonatal

snakes. If using frozen-thawed prey, care should be taken to ensure that the rodent isthoroughly thawed and is at a temperature similar to what would be considered normalfor a rodent (around 100�F, 38�C). Often, detection of a warm object will elicit a strikeand result in prehension and subsequent consumption of the prey item. Another usefultrick is to incise the nose or head of the rodent to expose blood and tissue. This

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theoretically increases the presence of volatile material, which entices interest and astrike from the snake.“Tease feeding” is another method that is used, especially with defensive arboreal

species that will readily strike out and attempt to bite things that are disturbing them.Essentially, this practice involves eliciting a reflexive instinct that causes the snake toswallow the prey item once it is in their mouth. The prey item is held in a pair of forcepsand used to annoy the snake until it strikes at, bites, and constricts or holds onto it.This procedure often requires multiple attempts and the key is holding still after thesnake bites and holds onto the prey item. As previously mentioned, with some animalseven slowly trying to back away can disturb the animal and redirect their attentioncausing them to drop the prey item.If none of the aforementioned methods is successful, offering live rodents may be

warranted. In the case of neonatal snakes, this usually means offering young pinkiemice and rats. Rodents this young present no danger compared with older rodentsso there is no real downside to feeding live pinkies from the perspective of reptilehealth and safety. However, rodent welfare should not be ignored. The author con-siders the death of young rodents from hypothermia, dehydration, and/or starvationon the floor of an anorexic reptile’s enclosure unacceptable.Feeding neonatal snakes natural prey such as frogs, toads, and lizards is certainly a

possibility if necessary or desired. It can be effectively argued this is a healthier andmore natural approach to captive nutrition. The only reason rodents are preferredas food for captive snakes is availability and expense. Rodents are relatively cheapand plentiful. Though less available than rodents, “feeder” amphibians and lizardscan be obtained through many dealers. In North America, invasive or common speciesare often collected and sold as feeder animals. Cuban tree frogs (Osteopilus sp), Med-iterranean house geckos (Hemidactylus turcicus), and Anolis sp are frequently avail-able. Feeder animals that are collected in the wild should be quarantined andscreened properly to minimize the risk of disease transmission. Humane euthanasiaand freezing for a period can help minimize, but does not completely negate, therisk of pathogen transmission.In cases in which seemingly natural prey is offered, neonates may still stubbornly

refuse to feed voluntarily. In these cases, experience suggests that it is best to beginassist feeding sooner rather than later. If assist feeding is delayed too long, manyanimals can become debilitated to the point at which intervention is futile. Variousoptions exist for assist-feeding neonatal snakes. The first and easiest is the admin-istration of a commercially available liquid diet. Whole prey items can be pureed andadministered via the same method. Extruding devices, commonly referred to as apinkie pumps, have been used for years by hobbyists to easily administer wholeprey items to anorexic animals. Obviously, use of these tools necessitates humaneeuthanasia of the prey animal before administration. Another typically used methodis assist feeding whole or large pieces of prey items. Adult mouse or rat tails are wellsuited for this purpose because of their shape. Obviously, rodent tails are not anappropriate long-term diet, but are suitable for the first few feedings if necessary.In these cases, the animal is well restrained and a lubricated food item is introducedinto the oral cavity (Fig. 4). In some cases, the animal will instinctively swallow theprey from that point. The key to this procedure is hooking the teeth into the preyitem so the snake cannot easily drop it. If the animal will not swallow the item volun-tarily, it will need to be pushed down to the esophagus or stomach. This procedureshould be approached with great care because it is easy to traumatize the reptile’supper gastrointestinal tract. In addition, some snakes will resist vigorously. If theprocedure is not quickly completed, the negative effects of the stress the animal

Fig. 4. Assist feeding a prekilled pinkie mouse to a young tiger ratsnake (Spilotes pullatus).The prey was introduced into the oral cavity and the snake was returned to its enclosurewhere it voluntarily swallowed the mouse.

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experiences can outweigh the benefit of the feeding. If at any point during thefeeding the animal noticeably weakens, the procedure should be aborted and futureattempts should be modified to be less traumatic (eg, better restraint, smaller fooditem).Some species of snakes are notoriously difficult to establish following birth or hatch-

ing. The author maintains a collection of pythons from the genus Antaresia (Children’s,Stimson’s, spotted, and pygmy pythons). These pythons make excellent captivesbecause they are small, hardy, and often docile; however, the neonates can be chal-lenging to work with. Patience and persistence will usually pay off but it can take manyweeks to establish consistent voluntary feeding and, with clutches of 10 to 20 eggs,the commitment to succeed can be daunting. As an alternative, the author has foundthat, almost without fail, if neonatal Antaresia pythons are assist-fed a portion of apinkie mouse following their first ecdysis, they will begin feeding voluntarily thereafter.Several other species respond similarly; therefore, if properly performed, thisapproach can be very effective. Not all species, or individual animals, will respondquickly to this technique. The author has worked with animals that have been anorexicfor longer than a year following hatching or birth but eventually begin feeding vigor-ously on their own. Most memorably, a neonatal female green anaconda (Eunectesmurinus) steadfastly refused food for almost 18 months. The snake was assist fedone to two appropriately sized mice or young rats every 7 to 10 days. Growth wasreduced compared with voluntarily feeding littermates but it was appreciable. Beforeevery assisted feeding, a rodent was presented with tongs to give the snake the op-portunity to feed. One day the anaconda prehended and constricted the rodent enthu-siastically and ever since it has fed voluntarily with gusto.

TIPS AND TRICKS FOR FEEDING CAPTIVE REPTILESMonitors and Other Large, Carnivorous Lizards

Obesity with its associated complications is epidemic in captive monitor lizards. Amonitor lizard in the wild is usually an extremely different beast from the sedentary,

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football-shaped lizards that are typically seen as pets. Wild monitors are typically lean,active hunters that feed opportunistically on almost anything they can run down and fitin their mouths. Captive monitors are typically fed diets consisting exclusively of lab-oratory rodents that are dangled right in front of their noses, whereas wild monitorsconsume a wide variety of food items that they have to work to capture. The naturaldiet of monitor species in the wild consists mostly of invertebrate prey but also in-cludes eggs, fish, amphibians, and other reptiles. Mammals and birds are present inthe natural diet but at very low levels.17–19 The author has seen many obese monitorlizards with chronic colonic impactions consisting almost entirely of rodent hair. Notonly does the colon become massively distended with feces, the development oftranscolonic membranes will frequently concurrently occur.20 Savannah monitors(Varanus exanthematicus) typically present with this disorder; therefore, when manag-ing cases of constipation or obstipation in this species, colonic patency should alwaysbe verified early in the diagnostic investigation. Often, these cases are intractable totreatment by the time they are presented to a veterinarian. However, it is possiblethat these problems could be prevented with implementation of a more natural dietand increased exercise.The author recommends as varied a diet as possible for captive varanid lizards,

ideally consisting of at least 50% invertebrate prey. In addition, efforts should bemade to encourage the animals to forage and expend energy. This can be accom-plished with a variety of methods and keepers are encouraged to use their imagina-tion. Minimally, if using prekilled rodents, chicks, or eggs, the prey items can beplaced in various areas within the enclosure forcing the animal to forage. Invertebrateprey, such as crickets, mealworms, and cockroaches, are typically presented aliveand require physical effort to capture them. Making the commitment to provide adiet such as this for a captive monitor lizard is difficult but rewarding because of thepotential positive effects for the animal.

GRASSLAND TORTOISES

It is important to recognize that not all tortoise species require the same diet. A com-mon mistake is to offer diets that are too rich to grassland species such as leopard(Geochelone pardalis) and sulcata (G sulcata) tortoises. These tortoises will greedilyconsume large amounts of fruit and vegetables (not to mention animal protein andwaste, if given the opportunity); however, in the wild they rarely encounter suchfood items and eat most low-quality grasses and vegetation. A grassland tortoiseon an appropriate diet consisting of more than 90% grass will have formed, relativelydry, droppings, which are composed mostly of compressed stems. Compare this to atortoise that receives large amounts of chopped fruits, vegetables, and leafy greens,which will have loose and smelly droppings.Grassland tortoises will usually feed daily in the wild but in captivity many are offered

food only a few times a week. Much like small herbivores such as rabbits and rodents,constant grazing is beneficial for the gastrointestinal function and health of grasslandtortoises. A healthy well-fed sulcata tortoise will have ingesta and feces in the entiretyof its gastrointestinal tract at all times.Many well-intentioned keepers will offer grass hays to their captive tortoises directly

from the bale. The choice of food is correct but the method of presentation can causeproblems. When offered cut hay, tortoises often ingest entire (indigestible) stemsintact. These stems can accumulate and result in gastrointestinal impactions, espe-cially in smaller animals. When grazing naturally, tortoises will tear the stems asthey pull a mouthful away from the rooted plant, creating a much shorter and more

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manageable strand length. A simple way to avoid problems with stem length is to chopthe hay before offering it to the tortoise. A good rule of thumb is not to feed stemslonger than the length of the tortoises’ plastron.

FEEDING FREQUENCY

Most captive reptiles are not fed on a daily basis. As previously discussed, the theorybehind this feeding strategy is that, as ectotherms, reptiles do not require daily caloricintake and their relatively infrequent feeding is healthy or at least not detrimental. Withthe exception of some snakes, crocodilians, and lizards that binge and ingest preyitems that are gigantic relative to their body size, most reptiles will eat daily during theiractive times of the year if possible. In animals that naturally eat more frequently, thedown-regulation of gastrointestinal function is much less dramatic between mealscompared with “binge” eaters.21 Therefore, these animals commit relatively morecaloric resources toward maintenance of their gastrointestinal tracts in betweenmeals. As a result, insectivorous and small omnivorous or herbivorous lizards and tur-tles do well when fed daily. Even giant snakes do well in captivity when fed smallerfrequent meals versus occasional large meals. It is the author’s impression that snakesfed in this manner are more active and maintain better body condition compared withthose fed large prey infrequently. It is possible to create overweight animals regardlessof feeding frequency, thus growth and/or body condition must be continually moni-tored and the amount of food offered per feeding adjusted accordingly.

SUMMARY

Nutritional support is an important, though often neglected, factor in the managementof sick and anorexic reptiles. Reptiles can greatly benefit from receiving appropriatenutritional support in a timely manner. A basic understanding of reptilian metabolism,digestive physiology, and the natural history of commonly encountered species canhelp the clinician make sensible recommendations for the maintenance of healthyanimals and appropriate intervention in the case of ill animals.

REFERENCES

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